Problem: $ { \left[\begin{array}{rrr}{-1} & {0} & {0} \\ {2} & {1} & {4}\end{array}\right]+\left[\begin{array}{rrr}{2} & {1} & {2} \\ {4} & {-2} & {-1}\end{array}\right] = {?} } $
Answer: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{-1}+{2} & {0}+{1} & {0}+{2} \\ {2}+{4} & {1}+{-2} & {4}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{1} & {1} & {2} \\ {6} & {-1} & {3}\end{array}\right]}$